The present invention relates to a system for turning a swivel that forms a rotating connection between one or more risers and a piping system on a production vessel, a platform or the like for the production of oil or gas, and including a stationary part connected with a rotary drilling rig or the like on the vessel and one or more parts pivotally mounted in relation to the stationary part and connected to the vessel.
Systems for turning such a swivel aboard a production vessel for oil extraction at sea are known, but are of relatively small dimensions and weights, and have low operating pressures. Such a conventional system is furnished with a single drive arm attached to a lower part of the swivel and controlling rotary motion between the stationary part and the lower, rotating part of the swivel and transmits motion to other parts of the swivel by means of shear stress connections. Such system works well at relatively low production pressures and fluid volumes, in calm waters and at shallow to medium sea depths, but has disadvantages at high production pressures, high fluid volumes and in turbulent waters. In such conditions the swivel weight may be 100-150 tonnes and operational safety requirements are very high. For such large, heavy swivel systems the conventional turning systems are not suitable because the dimensions of the drive arm and the shear stress connections are very large and interfere with other equipment on the rotary drilling rig.